PROVENANCE IS IMPORTANT
For years, the Palos Park Tree Body
has advocated the planting of native species of trees, using the logic
that species native to our area have a proven ability to exist here, with
our cold winter temperatures and unpredictable summer rainfall. While
getting the species correct is a big first step in tree selection, that wonít
do you much good if you donít get the provenance right as well.
Provenance is a fancy way to say "place of origin." Where the
treeís ancestors evolved determines many of its genetic characteristics.
A tree grown here from a Bur oak acorn picked up in Texas has a Texas
provenance because its heredity was determined there. Heredity is
important because many subtle mutations develop through the years, as the
trees with the gene and the appropriate trait survive.
When we talk about the provenance of a
tree, we are not talking about the species as a whole, we are talking
about the specific tree. Before you purchase that tree, ask about where
the tree was grown, its place of origin. If it was locally grown from
local seed, it would be from the same latitude, the same relation to Lake
Michigan, and similar soil characteristics as where you plan to plant it,
so your chance for success would be good. Experts say that up to one
hundred miles is an acceptable distance; however, trees from Northern
Michigan sometimes have a problem on this side of the lake. Obviously, if
your new tree is from South Carolina or Georgia, it probably will not make
it through a winter freeze or a summer drought here.
The effect of provenance is easily
illustrated by experience with the planting of the sugar maple, Acer
saccharum. A sugar maple with a northern provenance will show low
drought resistance, susceptibility to leaf injury, but have high
resistance to winter injury. A tree with a southern provenance will show
high resistance to drought and leaf scorch, and have a low resistance to
winter injury. A tree with a central provenance will show a high
resistance to drought, a moderate resistance to leaf scorch, and high
resistance to winter injury. Obviously, this would be most appropriate for
our cold winter temperatures and unpredictable summer rainfall.
For several years, the trees planted by the
Village have been purchased from a grower who collects seeds locally and
raises them nearby. As a result, there has been a very high survival rate
of these trees planted on Village property.